Biology Reference
In-Depth Information
substrates were fine silt and clay deposited by the tributaries creating a large number of
relatively shallow sloping sand bars especially during low water seasons (February to June).
The sand bars deflect the river flow and create eddy counter-current systems. Another type of
primary habitat was deep pools, each pool with an eddy counter-current system due to
hillocks in the mid channel or hard rocks jutting out. This creates deep zone and meandering
of the river at Munger, Sultanganj and Kahalgaon. The river flow in a single channel with
meanderings formed marginal habitats downstream. Dolphins were also frequently sighted in
large groups in counter-current pools induced by bridge pilings at Patna and Bhagalpur, and
the monadnocks (rock islands) at Munger and Kahalgaon, and below the confluence of
Ghaghara, Gandak and Kosi at Doriganj, Patna and downstream of Kahalgaon, respectively.
Large counter current pools were also the primary sites for fishing, ferry crossings, and
religious and domestic bathing. The same conditions that make these areas suitable for
dolphins (i.e. hydraulic refuge and abundant fish), also make them desirable sites for human
use.
The higher counts for the upstream surveys can be explained by the greater number of
opportunities to detect surfacing dolphins at a slower surveying speed. The relatively large
number of sightings missed by the primary observers but detected by secondary observers
indicates that the actual number of dolphins occurring in the stretch of the Ganges under
study is probably greater than our minimum abundance estimates (Marsh & Sinclair, 1989),
even though we included the secondary observer sightings.
Conservation Status of the Ganges River Dolphins
The Ganges dolphin is listed in CITES Appendix 1. All of the Asian river dolphins have
suffered dramatic declines in both their range and numbers over the last three decades to the
point at which they rank as some of the most endangered of all mammals. In addition to
CITES listings, the IUCN-World Conservation Union has classified the
susu
as an
endangered species in 1996. Furthermore, the Ganges River dolphin has been included as a
Schedule-1 animal under the Indian Wildlife (Protection) Act 1972.
The future of Ganges dolphins appears to be bleak unless action is taken immediately to
reduce pressure on their freshwater ecosystems. They face unprecedented threats through the
exploitation of freshwater river systems by people, causing high incidental mortality. In order
to prosper, the dolphin ironically requires the same conditions as people who use the river,
namely, a healthy, flowing, living river.
Threats
The Ganges dolphins face many threats -incidental capture in fisheries (by catch),
depletion of food resources, chemical and noise pollution, habitat destruction, over-fishing
and climate change, and in some cases, directed killing for oil and meat.
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